Behavioral Neuroscience Summers

Turtle Eyeblink Behavior Sensory Stimulation of Eyeblink Eyeblink Motor Output Neuromuscular Function In vitro Conditioning

text:Kandel pages 1243 & 849 Glu ACh BDNF Turtles and Ecology Eyeblink Circuitry end     Acronyms/Abbreviations     Syllabus

Eyeblink Conditioning
I. Pond Turtles  			

	A. Chrysemys picta (Painted Turtle) or C. scripta (Red-eared Pond Slider) are relatively large 
	    aquatic turtles
	
		1. Habitat: slow moving shallow streams, sluggish rivers, 
		   swamps, ponds, lakes
		
			a. soft bottoms, vegetation, half submerged logs
	
			b. C. picta = most widespread turtle in North America
			
				i. bicoastal in the north, eastern in south
				
					(1) few populations in SW
				
			c. C. scripta = eastern U.S. - Virginia to Brazil

		
		2. reptiles in freshwater habitats with few amphibious habits 
	
			a. unlike other turtles cannot derive much O2 from water
			
			b. court in the water
			
				i. lay eggs in moist pits on land
			
			c. bask in the sun
			
				i. to increase metabolic rate
			
			d. use celestial cues for directional guidance
	
		3. herbivorus as adults
		
			a. juveniles eat insects and other invertebrates
			
		4. very long lived
		
			a. sexual maturity only after 2-8 years	
		
		5. Evolutionarily very old - Miocene > 5(10)6 years
		Cenozoic Era 65 mya - present, Tertiary Period 65-1.8 mya, Miocene Epoch 23-8-5.3 million years ago
		
	B. Turtle Eye Blink
	
		1. nictitating membranes, or 3rd eyelids
		
			a. addition to their normal eyelids  in some animals
			
				i. turtles and some mammals 
	
			
		2. Aquatic environments with vegetation have a variety of potential
		    hazards for the eyes
			
			a. nictitating membranes are translucent but protective
	
			
		3. in response to a corneal stimulus
		
			a. imagine entering the water
			
			b. or some dust on an air current moving toward the eye

 
		4. the eyeball is retracted into the orbit 
					and
					
		5. the nictitating membrane is actively moved across the eye
		
			a. by the pyramidalis and quadratus muscles
						
			b. eyeball retraction is not required for the blink
	
			
		6. most experiments use an airpuff to the cornea of rabbits or cats
		
			a. the blink is a passive sweeps across the eye
			
			b. due to retraction of the eye by extraocular muscles
	
		
			
II. Eye Blink Reflex (rabbits, cats, mice)

	A. Sensory information from the face 
	
		1. Trigeminal nerve afferents
		
			a. opthalmic branch
			
			b. to the spinal fifth cranial/trigeminal nucleus
	
	B. One interneuron in trigeminal complex
	
		1. nucleus oralis
		
			a. disynaptic pathway
	
	C. stimulate accessory abducens nuclei motor nerve fibers
	
		1. innervate retractor bulbi muscle
		
			a. contraction pulls eye into socket
			
				i. passive blink
		
	D. trigeminal also stimulates facial, principle abducens,
	    oculomotor and trochlear nuclei
	
		1. facilitates eye retraction
		
			a. simultaneous contraction of all extraocular muscles 
			     (except superior oblique)
			
		2. turtles don't have orbicularis oculi muscle
		
			a. \ facial nerves not involved
	
	
	E. Conditioning: US = airpuff, CS = sound
	
		1. training pair airpuff with sound
		
		2. CR = rabbit will blink to sound alone
	
		3. Cerebellum is important for conditioning
		
			a. lesions in cerebellum disrupt the acquisition and
			    retention of a classically conditioned eyeblink reflex
				
				i. lesion to cerebellar vermis abolishes CR but not UR
				
					(1) learning depedendent activity of vermis 
					     neurons parallel conditioning
				
				ii. lesion to deep interpositus nucleus
				      of the cerebellum also abolishes CR